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Old 16th May 2019, 7:00 pm   #54
JohnBHanson
Heptode
 
Join Date: Aug 2009
Location: Worthing, Sussex, UK.
Posts: 661
Default Re: Gemini 80-Bus System

Just checked there is a mix up in the SERST routine. For console this should be the status of input characters. For printer devices it is the status of the output.

The console status in the bios incorrectly returns the output status rather than the input status. However it is a common routine that is used for both printer and console so a simple patch is not sensible.

however if you want to patch it to work for console - at the sacrifice of the printer routines working (very few things use the printer status) patch address 0f6ef from 20h to 01h.
(Address given for 64k version) change first two digits of address accordingly.

Attached is bios listing for your reference..... Note you have to add the bios base addresses to those given in the listing. You can find the bios easy on disk by looking for
c3 xx xx repeated 11 times starting either at the start of a sector of half way through a sector (512 bytes).

xx xx will be different for each repeat.
Attached Files
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